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Lunev" Cc: "Denis V. Lunev" , qemu-devel@nongnu.org, qemu-block@nongnu.org, Vladimir Sementsov-Ogievskiy , John Snow , Andrey Drobyshev Subject: Re: [PATCH v3 0/9] block: cheaper zero handling in backup and commit Message-ID: References: <20260929155125.3151111-1-den@openvz.org> <127bf797-defd-46bf-9aa2-063f15152cfc@virtuozzo.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <127bf797-defd-46bf-9aa2-063f15152cfc@virtuozzo.com> User-Agent: NeoMutt/20260616 X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 Received-SPF: pass client-ip=170.10.129.124; envelope-from=eblake@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -22 X-Spam_score: -2.3 X-Spam_bar: -- X-Spam_report: (-2.3 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.24, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: qemu development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Mon, Oct 05, 2026 at 10:59:11AM +0200, Denis V. Lunev wrote: > On 9/29/26 17:51, Denis V. Lunev wrote: > > This email originated from an IP that might not be authorized by the domain it was sent from. > > Do not click links or open attachments unless it is an email you expected to receive. > > Backup and commit re-query the source block status for every task and > > size a task by the copy buffer, so a long run of zeroes turns into a > > crowd of small write-zeroes requests. This series reuses what the > > up-front scan already learned and lets one write-zeroes task cover a > > whole run. > > > > Backup of a 16G qcow2 image holding 1G of data, the rest never > > allocated, sync=full to a raw target on ext4: > > > > tasks time > > before 16384 1.6s > > after 1088 1.0s > > > > Such an image is the normal case rather than a corner one: a guest with > > discard enabled on a disk which is mostly free leaves exactly this > > shape behind. > ping It looks like this series is fully reviewed; I also took a look at it and didn't spot anything to add. I plan on queueing into a pull request shortly. -- Eric Blake, Principal Software Engineer Red Hat, Inc. Virtualization: qemu.org | libguestfs.org